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Steve Chiotakis: Congress begins hearings today on the huge Gulf of Mexico oil spill.
A lot of blame is going around. Meanwhile, BP once again will try to plug the biggest leak with a contraption called a top hat. Now BP's been spraying something called Corexit onto the spill, a chemical that breaks up the slick into tiny droplets that sink underwater. But it, like the oil, presents a lot of problems. Jill Barshay reports.

Jill Barshay: BP is hoping that Corexit will prevent oil from washing ashore and destroying fragile wetlands. But Richard Charter of Defenders of Wildlife worries that dispersed oil will get eaten by fish and end up in the food chain.

Richard Charter: The oil's toxic. The dispersant is toxic. And the combination is toxic. The whole thing is turning this particular piece of water into a giant chemistry experiment.

Nalco is the company that makes Corexit. Charlie Pajor is a spokeman:

Charlie Pajor: Everything is toxic in depending on how much you have. And when properly applied, it is less toxic than the oil itself.

But there's no independent confirmation of that. Nalco isn't required to publicly disclose what's in Corexit for competitive reasons. Environmental activists like Charter say we don't have better options to protect the shoreline. That explains why BP has bought Nalco's entire stockpile of Corexit and put in orders for a lot more.